Bicycling is recognized by the avid mountain and road cyclists riding on hilly or mountainous terrain or by the average or “Sunday” rider as a particularly effective type of aerobic exercise. Also, bicycling provides a low impact type of exercise which is especially easy on the knees and feet. As a result, stationary exercise bicycles facilitating this type of exercise are popular for both home and health club use.
Conventional crank assemblies for stationary exercise bicycles usually include a drive pulley that in turn is connected by a belt or a chain to a load device such as an alternator or mechanical brake in order to provide resistance to the user's pedaling. These crank assemblies often include fastener-holes formed in the drive pulley, a crank hub, and an elongated crank arm which has an upper portion formed integrally with the drive pulley and a lower end portion formed with a threaded hole in which a pedal of the stationary exercise bicycle is mounted. The drive pulley has a central opening that permits a fixed rotating shaft to extend therethrough in such a manner that the drive pulley can rotate synchronously with the pedal. Screws are inserted through the fastener-holes of the drive pulley and the crank arm, thereby completing assembly of the conventional crank assembly.
Note: that it is difficult to repair and maintain the conventional crank assembly as a result of the above described construction. When repair or maintenance of the conventional crank assembly is required, the entire assembly including the drive pulley, the crank hub and the elongated crank arm must be disassembled. In addition to substantially increasing manufacturing and repair expense, the conventional crank assembly tends to be noisy. As a result, the crank hub frequently becomes loose and requires frequent maintenance. Thus, it is desirable to decrease the manufacturing expense, reduce maintenance costs and decrease noise of stationary exercise bicycle apparatuses.
With respect to operation of exercise bicycles, research has shown that the optimum position seating for bicycling is for the seat to be at a height that allows for approximately 15 degrees of leg bend when the rider's foot is at the lowest pedal position and for the seat post to be positioned rearwardly of the pedal crank and along a line passing through the pedal crank at an angle of approximately 71 degrees from the horizontal. Thus, the seat positioning requirements for optimum performance vary greatly from rider to rider.
It has also been found that even slight movements of seat position will work either different muscles and/or different parts of the muscles. Typical seat position mechanisms provide only widely spaced adjustments which can limit the user's ability to comfortably work different muscles.
In view of these issues and others, it is clear that a highly adjustable seat positioning system is needed, one that is easily controlled. The most common form of seat adjustment involves using a pin, usually secured to the exercise bikes frame and often spring loaded, that is inserted into one of a number of holes in the seat post in order to position the seat. However, this arrangement has a number of disadvantages including the necessity of dismounting the bike to pull the pin out and because of the spacing of the holes on the post, the seat can only be positioned in increments that are on the order of one inch. One approach to solving this problem has been implemented on an exercise bicycle manufacture by Cybex Intl. of Medway, Mass. In this product, the seat post is configured with openings having a flap portion bent inwardly on the lower edge each of the openings which permit the user to pull the seat up to a new position without pulling the pin out. This arrangement provides a ratchet effect in that the flaps will guide the pin out of the openings while the seat post is moving up. However, it is still necessary for a user to manually pull the pin out to lower the seat. Also, the shape of the openings results in vertical seating increments of at least one inch.